Piezoelectric film nozzle and ink-jet printing equipment

Abstract

The invention relates to the technical field of ink-jet printing, in particular to a piezoelectric film spray head and ink-jet printing equipment, and the piezoelectric film spray head comprises a first ink inlet flow channel, an ink return flow channel and a plurality of first ink cavities which are all arranged in the spray head; each first ink cavity comprises an ink jet preparation cavity, an ink cavity elastic vibration plate, an ink inlet throttling part, an ink return throttling part and a jet hole, the first ink inlet flow channel is communicated with the ink jet preparation cavity through the ink inlet throttling part, and the ink return flow channel is communicated with the ink jet preparation cavity through the ink return throttling part; the ink cavity elastic vibration plate is used for extruding the ink jet preparation cavity to enable ink to be jetted out from the jet hole, a first isolation hole is formed in the bottom face of the ink inlet throttling part, and the first isolation hole communicates with the external space and the ink inlet throttling part. The first isolation hole is communicated with the external space and the ink inlet throttling part, so that pressure residual waves and clutters of inner and outer cavities of ink are quickly eliminated, and inner and outer pressures of an ink squeezing cavity of the nozzle are quickly balanced.

Description

Technical Field

[0001] The invention relates to the technical field of inkjet printing, in particular to a piezoelectric film nozzle and an inkjet printing device. Background Art

[0002] In piezoelectric inkjet printing, the elastic vibration plate in the ink chamber will deform under the action of the piezoelectric film, which will transmit the pressure change to the ink in the inkjet preparation chamber. This pressure change causes the ink inside the nozzle to vibrate, and the speed of the vibration will be toward the outside of the nozzle. Due to this vibration, the semi-lunar curved surface of the ink in the nozzle will squeeze outward, eventually forming an ink column.

[0003] However, the residual oscillation of the flow velocity at the nozzle will lead to the generation of satellite droplets. Satellite droplets refer to additional small ink droplets generated due to vibration and pressure fluctuations in addition to the normally ejected ink droplets. The existence of these satellite droplets will affect the volume uniformity of the ejected droplets and thus affect the printing quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0005] The solution of the present invention to its technical problem is: a piezoelectric film nozzle, which includes a first ink inlet channel, an ink return channel and a plurality of first ink cavities, all of which are arranged inside the nozzle, each of the first ink cavity includes an inkjet preparation cavity, an ink cavity elastic vibration plate, an ink inlet throttling portion, an ink return throttling portion and a nozzle hole, the first ink inlet channel is connected with the inkjet preparation cavity through the ink inlet throttling portion, the ink return channel is connected with the inkjet preparation cavity through the ink return throttling portion, the ink cavity elastic vibration plate is arranged at the top of the inkjet preparation cavity, the nozzle is arranged at the bottom of the ink return throttling portion, the ink cavity elastic vibration plate is used to squeeze the inkjet preparation cavity to make the ink spray out from the nozzle, the bottom surface of the ink inlet throttling portion is provided with a first isolation hole, the first isolation hole connects the external space with the ink inlet throttling portion

[0006] The beneficial effects of the present invention are as follows: ink flows in from the ink inlet flow channel, flows into the inkjet preparation cavity through the ink inlet throttling portion; the ink is squeezed under the deformation of the elastic vibration plate of the ink cavity, and the ink drips out from the nozzle hole at the bottom of the ink return throttling portion through the ink return throttling portion; at the same time, the remaining ink flows into the ink return flow channel through the ink return throttling portion, and the ink return flow channel recycles the ink; the first isolation hole connects the external space with the ink inlet throttling portion, thereby quickly eliminating the residual noise of the pressure inside and outside the ink cavity, realizing the rapid balance of the pressure inside and outside the ink squeezing cavity of the nozzle, reducing the unstable factors in the ink ejection process, and thus improving the stability and reliability of printing.

[0007] As a further improvement of the above technical solution, the ink inlet throttling portion includes a flow limiting portion and a drainage portion, the drainage portion is connected to the ink return channel, the flow limiting portion is connected to the inkjet preparation cavity, the channel cross-sectional area of ​​the flow limiting portion is smaller than the channel cross-sectional area of ​​the drainage portion, and the first isolation hole connects the external space with the drainage portion.

[0008] As a beneficial effect of further improvement of the above technical solution, the flow limiting portion increases the fluid damping when the ink flows from the inkjet preparation cavity to the ink inlet throttling portion. Even when the ink is squeezed, the equilibrium state of the ink in the first isolation hole will not be destroyed, ensuring that the air pressure can be balanced in the first isolation hole. At the same time, the ink will not flow out of the first isolation hole due to pressure changes, thereby improving the stability and reliability of the entire inkjet system.

[0009] As a further improvement of the above technical solution, the first isolation hole is conical, and the width of the first isolation hole gradually decreases from the top of the first isolation hole to the bottom of the first isolation hole.

[0010] As a further improved beneficial effect of the above technical solution, the principle of capillary action is utilized. During the operation of the inkjet printing system, when the ink is subjected to a certain pressure inside the nozzle, due to the existence of the flow limiting portion, it is difficult for the ink to flow out directly through the first isolation hole. The gradually narrowing design of the first isolation hole further enhances its blocking effect on the ink, ensuring that the ink can be effectively locked inside the nozzle even under high pressure, avoiding unnecessary leakage, and ensuring the sealing and safety of the system.

[0011] As a further improvement of the above technical solution, the ink return throttling portion is a cylindrical cavity, and two ink return interfaces are provided at the bottom end of the ink return throttling portion. The two ink return interfaces are arranged along the tangent of the bottom end of the ink return throttling portion, and the ink return interfaces connect the ink return throttling portion and the ink return flow channel.

[0012] As a beneficial effect of further improvement of the above technical solution, the two ink return interfaces are arranged along the tangent direction of the bottom end of the ink return throttling portion, ensuring smooth connectivity between the two ink return interfaces and the internal space of the ink return throttling portion and the ink return flow channel. When the ink passes through the ink return throttling portion, the ink can form an orderly outflow pattern along the side wall of the ink return throttling portion, thereby improving the flow efficiency of the ink and reducing the generation of turbulence and bubbles during the flow of the ink, thereby ensuring a stable supply of ink and improving printing quality.

[0013] As a further improvement of the above technical solution, the first ink cavity further includes a second isolation hole, which is arranged at the connection between the ink return interface and the ink return channel, and the second isolation hole is connected to the external space.

[0014] As a beneficial effect of further improvement of the above technical solution, the second isolation hole is directly connected to the external environment, constructing an efficient sound wave energy discharge channel, which can quickly guide the sound wave energy accumulated inside the ink to the external environment, reduce sound wave reflection and clutter interference, and thus improve the operating efficiency and stability of the entire system; in addition, this structural design helps to avoid unnecessary interference between adjacent ink cavities through the ink return channel and the ink return interface, thereby ensuring the uniformity of the ink and the printing quality.

[0015] As a further improvement of the above technical solution, the cross-section of the second isolation hole is rectangular, and the cross-sectional area of ​​the second isolation hole gradually decreases from the top of the second isolation hole to the bottom of the second isolation hole.

[0016] As a beneficial effect of further improvement of the above technical solution, the second isolation hole can ensure that the sound wave energy is quickly and effectively captured during the propagation process and is smoothly guided to the external environment along the tapered channel. This tapered structure also enhances the capillary effect of the channel, making the flow of ink inside the channel more stable and controllable, further improving the ventilation performance of the channel.

[0017] As a further improvement of the above technical solution, the spray hole is coaxially arranged with the ink return throttling portion, and the spray hole connects the ink return throttling portion with the external space.

[0018] As a beneficial effect of further improvement of the above technical solution, when the ink is pressurized in the cylindrical cavity, the pressure will be transmitted more evenly along the axial direction of the cavity. The nozzle is located on the main axis of this pressure transmission and can directly withstand and respond to large pressure changes from inside the cavity, making it easier for the nozzle to overcome surface tension under high-pressure conditions, thereby causing the ink to drip out of the nozzle in a more delicate and uniform manner.

[0019] As a further improvement of the above technical solution, the spray hole is conical, and the width of the spray hole gradually decreases from the top of the spray hole to the bottom of the spray hole.

[0020] As a further improved beneficial effect of the above technical solution, when the ink flows in from the top of the nozzle, its initial width is relatively large and can accommodate more ink. As the ink flows downward and approaches the bottom of the nozzle, the width gradually decreases, forcing the ink flow to accelerate and concentrate, thereby forming high-pressure, high-speed ink droplets at the nozzle outlet, which helps to control the flow speed and direction of the ink and ensure that the formation of ink droplets is more precise and consistent.

[0021] As a further improvement of the above technical solution, the piezoelectric film nozzle also includes a second ink inlet channel and a plurality of second ink cavities, the ink return channel is connected to the second ink inlet channel through the second ink cavity, and the first ink cavity and the second ink cavity are arranged at intervals.

[0022] As a further improvement of the above technical solution, the second ink cavity enhances the ink distribution and regulation capabilities of the nozzle, and the second ink cavity is staggered with the first ink cavity to construct a more complex and sophisticated ink flow network. By accurately controlling the amount of ink in each ink cavity and the timing of injection, a more sophisticated and high-quality printing effect can be achieved, providing more possibilities and flexibility for personalized customization and printing of complex patterns.

[0023] An inkjet printing device, characterized by comprising a piezoelectric film nozzle as described in any one of the above items.

[0024] The beneficial effects of the present invention are as follows: the ink inlet channel of the piezoelectric film nozzle is connected to the ink inlet box of the inkjet printing device, and the ink return channel of the piezoelectric film nozzle is connected to the ink return box of the inkjet printing device, ensuring the smooth supply and recycling of ink, thereby improving the printing efficiency and the ink utilization rate; the piezoelectric film nozzle can quickly eliminate the pressure residual waves and noise in the inner and outer cavities of the ink by adding the design of the isolation hole, which helps to achieve a rapid balance of the pressure inside and outside the ink squeezing cavity of the nozzle; especially in the OLED printing process, there are extremely high requirements for the uniformity of the ink droplet volume, and this pressure balance helps to improve the uniformity of the droplet volume spit out by the nozzle of the nozzle, thereby ensuring the stability and reliability of the printing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is one of the structural schematic diagrams of the present invention;

[0026] Figure 2 This is the second structural schematic diagram of the present invention;

[0027] Figure 3 It is a structural schematic diagram of an embodiment of the present invention.

[0028] In the accompanying drawings: 1-first ink inlet channel, 2-ink return channel, 3-first ink cavity, 301-inkjet preparation cavity, 302-ink cavity elastic vibration plate, 303-ink inlet throttling part, 304-ink return throttling part, 305-nozzle hole, 306-first isolation hole, 307-flow limiting part, 308-flow guide part, 309-ink return interface, 310-second isolation hole, 4-second ink inlet channel, 5-second ink cavity. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the above briefly describes the drawings required for use in the description of the embodiments. Obviously, the drawings described are only part of the embodiments of the present invention, not all of the embodiments, and those skilled in the art can also obtain other design solutions and drawings based on these drawings without creative work.

[0030] The following will clearly and completely describe the concept, specific structure and technical effects of the present invention in combination with the embodiments and drawings, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present invention. In addition, all the connection / connection relationships mentioned in the text do not refer to the direct connection of components, but refer to the formation of a better connection structure by adding or reducing connection accessories according to the specific implementation situation. The various technical features in the present invention can be combined interchangeably without conflicting with each other.

[0031] In piezoelectric inkjet printing, the elastic vibration plate in the ink chamber will deform under the action of the piezoelectric film, which will transmit the pressure change to the ink in the inkjet preparation chamber 301. This pressure change causes the ink inside the nozzle to vibrate, and the speed of the vibration will be toward the outside of the nozzle. Due to this vibration, the semi-lunar curved surface of the ink in the nozzle will squeeze outward, eventually forming an ink column.

[0032] However, the residual oscillation of the flow velocity at the nozzle will lead to the generation of satellite droplets. Satellite droplets refer to additional small ink droplets generated due to vibration and pressure fluctuations in addition to the normally ejected ink droplets. The existence of these satellite droplets will affect the volume uniformity of the ejected droplets and thus affect the printing quality.

[0033] To this end, the present invention proposes a piezoelectric film nozzle, referring to Figure 1-2, which includes a first ink inlet channel 1, an ink return channel 2 and a plurality of first ink chambers 3, all of which are arranged inside the nozzle, each of the first ink chambers 3 includes an inkjet preparation chamber 301, an ink chamber elastic vibration plate 302, an ink inlet throttling portion 303, an ink return throttling portion 304 and a nozzle 305, the first ink inlet channel 1 is connected to the inkjet preparation chamber 301 through the ink inlet throttling portion 303, the ink return channel 2 is connected to the inkjet preparation chamber 301 through the ink return throttling portion 304, the ink chamber elastic vibration plate 302 is arranged at the top of the inkjet preparation chamber 301, the nozzle 305 is arranged at the bottom of the ink return throttling portion 304, the ink chamber elastic vibration plate 302 is used to squeeze the inkjet preparation chamber 301 to make the ink spray out from the nozzle 305, and the bottom surface of the ink inlet throttling portion 303 is provided with a first isolation hole 306, the first isolation hole 306 connects the external space with the ink inlet throttling portion 303.

[0034] The ink flows in from the ink inlet channel, passes through the ink inlet throttling section 303 and flows into the inkjet preparation cavity 301; the ink is squeezed under the deformation of the ink cavity elastic vibration plate 302, and the ink passes through the ink return throttling section 304 and drips out from the nozzle 305 at the bottom of the ink return throttling section 304; at the same time, the remaining ink flows into the ink return channel 2 through the ink return throttling section 304, and the ink return channel 2 recycles the ink; the first isolation hole 306 connects the external space with the ink inlet throttling section 303, thereby quickly eliminating the residual pressure noise of the inner and outer cavities of the ink, achieving a rapid balance of the pressure inside and outside the ink squeezing cavity of the nozzle, reducing the unstable factors in the ink ejection process, and thus improving the stability and reliability of printing.

[0035] When the vibration plate vibrates during operation, the ink will be subjected to corresponding pressure, and the pressure may be transmitted to the position of the first isolation hole 306. Therefore, in one embodiment, the ink inlet throttling portion 303 includes a flow restriction portion 307 and a flow guide portion 308, the flow guide portion 308 is connected to the ink return channel 2, the flow restriction portion 307 is connected to the inkjet preparation cavity 301, the channel cross-sectional area of ​​the flow restriction portion 307 is smaller than the channel cross-sectional area of ​​the flow guide portion 308, and the first isolation hole 306 is connected to the external space and the flow guide portion 308. The flow restriction portion 307 increases the fluid damping when the ink flows from the inkjet preparation cavity 301 to the ink inlet throttling portion 303. Even when the ink is squeezed, the balance state of the ink in the first isolation hole 306 will not be destroyed, ensuring that the air pressure can be balanced in the first isolation hole 306, and the ink will not flow out of the first isolation hole 306 due to pressure changes, thereby improving the stability and reliability of the entire inkjet system.

[0036] When the ink is subjected to pressure inside the nozzle, the first isolation hole 306 may leak. Therefore, in one embodiment, the first isolation hole 306 is conical, and the width of the first isolation hole 306 gradually decreases from the top of the first isolation hole 306 to the bottom of the first isolation hole 306. The principle of capillary action is utilized. During the operation of the inkjet printing system, when the ink is subjected to a certain pressure inside the nozzle, due to the existence of the flow restriction 307, it is difficult for the ink to flow out directly through the first isolation hole 306. The design of the first isolation hole 306 becoming gradually narrower further enhances its blocking effect on the ink, ensuring that the ink can be effectively locked inside the nozzle even under high pressure, avoiding unnecessary leakage, and ensuring the sealing and safety of the system.

[0037] Problems such as poor ink flow, accumulation of bubbles and impurities, and unstable ink supply may lead to reduced printing quality. Therefore, in one embodiment, the ink return throttling section 304 is a cylindrical cavity, and two ink return interfaces 309 are provided at the bottom of the ink return throttling section 304. The two ink return interfaces 309 are arranged along the tangent of the bottom of the ink return throttling section 304, and the ink return interfaces 309 connect the ink return throttling section 304 with the ink return flow channel 2. The two ink return interfaces 309 are arranged along the tangent direction of the bottom of the ink return throttling section 304, ensuring that the two ink return interfaces 309 can achieve smooth connectivity with the internal space of the ink return throttling section 304 and the ink return flow channel 2. When the ink passes through the ink return throttling section 304, the ink can form an orderly outflow pattern along the side wall of the ink return throttling section 304, thereby improving the flow efficiency of the ink and reducing the generation of turbulence and bubbles during the flow of the ink, thereby ensuring a stable supply of ink and improving the printing quality.

[0038] In the working process of the ink jetting system, especially when the ink passes through the ink return throttling section 304, the sound wave energy generated by the vibration plate often produces violent reflections in this narrow space, resulting in the appearance of interfering clutter, which will have a negative impact on the accuracy and uniformity of ink jetting. Therefore, in one embodiment, the first ink cavity 3 also includes a second isolation hole 310, and the second isolation hole 310 is arranged at the connection between the ink return interface 309 and the ink return channel 2, and the second isolation hole 310 is connected to the external space. The second isolation hole 310 is directly connected to the external environment, constructing an efficient sound wave energy discharge channel, which can quickly guide the sound wave energy accumulated inside the ink to the external environment, reduce sound wave reflection and clutter interference, and thus improve the operation efficiency and stability of the entire system; in addition, this structural design helps to avoid unnecessary interference between adjacent ink cavities through the ink return channel 2 and the ink return interface 309, ensuring the uniformity of the ink and the printing quality.

[0039] Inside the pore, the propagation of sound wave energy may cause reflection and scattering phenomena, which will have an adverse effect on the uniformity of the ink. Therefore, in one embodiment, the cross-section of the second isolation hole 310 is rectangular, and the cross-sectional area of ​​the second isolation hole 310 gradually decreases from the top of the second isolation hole 310 to the bottom of the second isolation hole 310. The second isolation hole 310 can ensure that the sound wave energy is quickly and effectively captured during the propagation process, and is smoothly guided to the external environment along the tapered pore. This tapered structure also enhances the capillary effect of the pore, making the flow of ink inside the pore more stable and controllable, and further improving the ventilation performance of the pore.

[0040] Uneven pressure transmission will affect the ink spraying effect. Therefore, in one embodiment, the nozzle 305 is coaxially arranged with the ink return throttling section 304, and the nozzle 305 connects the ink return throttling section 304 with the external space. When the ink is pressurized in the cylindrical cavity, the pressure will be transmitted more evenly along the axial direction of the cavity. The nozzle 305 is located on the main axis of this pressure transmission and can directly withstand and respond to the larger pressure changes from the inside of the cavity, making it easier for the nozzle 305 to overcome the surface tension under high pressure, so that the ink drips out of the nozzle 305 in a more delicate and uniform manner.

[0041] If there is inconsistency in the size of the ink droplets, the speed of the jetting, and other related parameters, it will have a negative impact on the quality of the printed image or text. Therefore, in one embodiment, the nozzle 305 is conical, and the width of the nozzle 305 gradually decreases from the top of the nozzle 305 to the bottom of the nozzle 305. When the ink flows in from the top of the nozzle 305, its initial width is relatively large and can accommodate more ink. As the ink flows downward and approaches the bottom of the nozzle 305, the gradual decrease in width forces the ink flow to accelerate and concentrate, thereby forming high-pressure and high-speed ink droplets at the outlet of the nozzle 305, which helps to control the flow speed and direction of the ink and ensure that the formation of ink droplets is more accurate and consistent.

[0042] During operation, refer to Figure 1-2. In this embodiment, four first ink chambers 3 are designed, and the ink inlet channel is connected to the ink inlet box. The ink is injected through the ink inlet channel and enters each first ink chamber 3 through diversion, and then flows into the inkjet preparation chamber 301; the elastic vibration plate of each ink chamber can be independently controlled to squeeze the ink through its deformation, and the squeezed ink passes through the ink return throttling part 304 and drips out from the bottom nozzle 305; the first isolation hole 306 connects the external space with the ink inlet throttling part 303 to quickly balance the pressure difference between the inner and outer chambers caused by the deformation of the elastic vibration plate and eliminate pressure fluctuations; the excess ink flows back through the reflux interface of the ink return channel 2 to achieve the recycling of the ink; the second isolation hole 310 at the bottom of the reflux interface is connected to the external environment, forming an efficient sound wave energy discharge channel, which can quickly guide the sound wave energy accumulated inside the ink to the external environment; the afterwaves generated by the impact of inks flowing out of adjacent reflux interfaces in the ink return channel 2 will also be released to the external space through the second isolation hole 310, thereby avoiding interference with the ink inside the ink return throttling part 304.

[0043] If the number of nozzles 305 is not sufficient, the problem of not being able to meet the fineness may occur when performing high-quality printing tasks. Figure 3 , the piezoelectric film nozzle also includes a second ink inlet channel 4 and a plurality of second ink cavities 5. The ink return channel 2 is connected to the second ink inlet channel 4 through the second ink cavity 5, and the first ink cavity 3 and the second ink cavity 5 are arranged at intervals. The second ink cavity 5 has the same structure as the first ink cavity 3, and will not be repeated here. The second ink cavity 5 enhances the nozzle's ability to distribute and regulate ink. The second ink cavity 5 and the first ink cavity 3 are staggered to construct a more complex and sophisticated ink flow network. By accurately controlling the amount of ink in each ink cavity and the timing of injection, a more sophisticated and high-quality printing effect can be achieved, providing more possibilities and flexibility for personalized customization and printing of complex patterns.

[0044] An inkjet printing device, characterized by comprising a piezoelectric film nozzle as described in any one of the above items.

[0045] The ink inlet channel of the piezoelectric film nozzle is connected to the ink inlet box of the inkjet printing device, and the ink return channel 2 of the piezoelectric film nozzle is connected to the ink return box of the inkjet printing device, ensuring the smooth supply and recycling of ink, thereby improving the printing efficiency and ink utilization rate; the piezoelectric film nozzle can quickly eliminate the pressure residual waves and noise in the inner and outer cavities of the ink by adding the design of isolation holes, which helps to achieve a rapid balance of the pressure inside and outside the nozzle ink squeezing cavity; especially in the OLED printing process, there are extremely high requirements for the uniformity of the ink droplet volume. This pressure balance helps to improve the uniformity of the droplet volume spit out by the nozzle of the nozzle, thereby ensuring the stability and reliability of the printing quality.

[0046] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A piezoelectric film nozzle, characterized in that: The nozzle comprises a first ink inlet channel (1), an ink return channel (2) and a plurality of first ink chambers (3), each of which is arranged inside the nozzle. Each of the first ink chambers (3) comprises an inkjet preparation chamber (301), an ink chamber elastic vibration plate (302), an ink inlet throttling portion (303), an ink return throttling portion (304) and a nozzle hole (305). The first ink inlet channel (1) is connected to the inkjet preparation chamber (301) through the ink inlet throttling portion (303), and the ink return channel (2) is connected to the inkjet preparation chamber (301) through the ink The ink return throttling part (304) is connected, the ink cavity elastic vibration plate (302) is arranged on the top of the inkjet preparation cavity (301), and the nozzle (305) is arranged at the bottom of the ink return throttling part (304). The ink cavity elastic vibration plate (302) is used to squeeze the inkjet preparation cavity (301) so that ink is sprayed out from the nozzle (305). The bottom surface of the ink inlet throttling part (303) is provided with a first isolation hole (306), and the first isolation hole (306) connects the external space with the ink inlet throttling part (303).

2. A piezoelectric film nozzle according to claim 1, characterized in that: The ink inlet throttling portion (303) includes a flow limiting portion (307) and a flow guiding portion (308), wherein the flow guiding portion (308) is connected to the ink return channel (2), and the flow limiting portion (307) is connected to the inkjet preparation cavity (301), and the channel cross-sectional area of ​​the flow limiting portion (307) is smaller than the channel cross-sectional area of ​​the flow guiding portion (308), and the first isolation hole (306) connects the external space with the flow guiding portion (308).

3. A piezoelectric film nozzle according to claim 2, characterized in that: The first isolation hole (306) is conical, and the width of the first isolation hole (306) gradually decreases from the top of the first isolation hole (306) to the bottom of the first isolation hole (306).

4. A piezoelectric film nozzle according to claim 1, characterized in that: The ink return throttling portion (304) is a cylindrical cavity, and two ink return interfaces (309) are provided at the bottom of the ink return throttling portion (304). The two ink return interfaces (309) are arranged along the tangent of the bottom of the ink return throttling portion (304), and the ink return interfaces (309) connect the ink return throttling portion (304) with the ink return flow channel (2).

5. A piezoelectric film nozzle according to claim 4, characterized in that: The first ink cavity (3) further comprises a second isolation hole (310), wherein the second isolation hole (310) is arranged at the connection between the ink return interface (309) and the ink return channel (2), and the second isolation hole (310) is connected to the external space.

6. A piezoelectric film nozzle according to claim 5, characterized in that: The cross section of the second isolation hole (310) is rectangular, and the cross-sectional area of ​​the second isolation hole (310) gradually decreases from the top of the second isolation hole (310) to the bottom of the second isolation hole (310).

7. A piezoelectric film nozzle according to claim 4, characterized in that: The spray hole (305) is coaxially arranged with the ink return throttling portion (304), and the spray hole (305) connects the ink return throttling portion (304) with the external space.

8. The piezoelectric film nozzle according to claim 1, characterized in that: The spray hole (305) is conical, and the width of the spray hole (305) gradually decreases from the top of the spray hole (305) to the bottom of the spray hole (305).

9. A piezoelectric film nozzle according to claim 1, wherein the piezoelectric film nozzle also includes a second ink inlet channel (4) and a plurality of second ink cavities (5), the ink return channel (2) is connected to the second ink inlet channel (4) through the second ink cavity (5), and the first ink cavity (3) and the second ink cavity (5) are arranged at intervals.

10. An inkjet printing device, characterized in that: It comprises a piezoelectric film nozzle as described in any one of claims 1-9.

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